INNOCENT UNTIL PROVEN GUILTY
Is that REALLY that hard to understand? Have you immigrated to this country in the past week? Are you that clueless to how our system works?
This is not an attack, it's an honest question. 4th graders should know this.

People don't have to PROVE innocence.

Obviously? Prove to me that he was an aggressor.
Prove to me BEYOND a reasonable doubt.

Have you listened to the 911 calls that Zimmerman made? He instigated the conflict by stalking an innocent kid.

Why wasn't Trayvon innocent until proven guilty?

That's a rhetorical question. He was murdered before he had a chance to go to court.